1. INTRODUCTION:

Microspheres are free-flowing powders made up of biodegradable proteins or synthetic polymers that range in size from 1 to 1000 nanometers. A well-designed control drug delivery system (CDDS) can solve some of the drawbacks of traditional therapy while also improving a drug’s therapeutic efficacy.¹

Drugs which eliminate faster from the intestine need to take frequently and also have drawbacks like gastric irritation so to rectify such difficulties floating microspheres are preferred and as they possess low density than gastric fluid hence it floats on the gastric fluid and perform constant and prolong release of drug that abolish the need of frequent dosing and as it releases the drug slowly so it doesn’t cause gastric irritation. It also maintains the effective concentration in the blood.²

Floating drug delivery are also considered as hydrodynamically balanced system, have swelling and expanding properties that’s why also known as swelling and expanding systems. These have polymeric coating hence also refer to be as polymeric bio adhesive systems and sometimes also called as high-density system.³

Microencapsulation is done to retard the release of drug, as shown in figure, drug is embedded in the polymeric capsule, when come in proximity of acidic gastric fluid with pH of 1.3, polymers get dissociate and the drug starts to release slowly and maintains a prolong release while attaining effective concentration.

Figure 1 depicting drug embedded inside polymeric core.

Floating microspheres are designed in such a manner that drug is embedded inside a polymeric core. Telmisartan is insoluble in aqueous media but can dissolve in various organic solvents and it is designed in such a way that it can release in the acidic environment of stomach.

Telmisartan is a class II nonpeptide angiotensin-converting enzyme inhibitor antagonist (AT1). It acts as a vasoconstrictor and relaxes the blood vessels. by specifically inhibiting angiotensin-aldosterone-secreting II's actions inhibiting its AT1 receptor binding in the adrenal gland and Smooth vasculature muscles Peak telmisartan concentrations (Cmax) are reached after oral dosing. the first one-hundredth of an hour Orally administered telmisartan has a nonlinear bioavailability (20-160 mg).^4,5

It is used for the treatment of moderate to severe cases of hypertension, heart diseases, heart attack. Telmisartan is available in the market under the class of antihypertensive drugs. Telmisartan drugs interact with renin and are used to regulate the central regulator of blood pressure as well as electrolyte homeostasis.⁶

Telmisartan is a good choice for treating hypertension because of its constant antihypertensive efficacy across the whole 24-hour dose interval and long-term BP-lowering effect, as well as its good tolerability profile. This is the reason why telmisartan is stated as the first-line treatment option for managing high BP.⁴

2. MATERIALS AND METHOD:

Materials:

Telmisartan was a gift sample from Psychotropic India Limited, Eudragit RS 100, Ethyl Cellulose, Polyvinyl alcohol, Sween 80, Sodium Chloride, Hydrochloric Acid, Chloroform, Methanol.

Method of Preparation:

The technique used is solvent evaporation technique. As the name suggests, firstly emulsion is formed. Weighted quantity of drug (telmisartan) and polymers (Eudragit RS 100 and ethyl cellulose) were dissolved in chloroform as telmisartan is insoluble in water so the medium preferred is chloroform in which both, the drug and polymers are completely soluble. Weighted quantity of drug is added in 10ml chloroform then polymer 1 is added and mixed followed by polymer 2. In the second step, aqueous phase is prepared in which 100ml distilled water is taken and 1.5 gm PVA is dissolved in it along with 0.3ml sween-80. This aqueous phase is allowed to stir at 300 RPM for half an hour on a magnetic stirrer so that PVA gets dissolved completely and a uniform mixture is formed.

In the third step, the dispersion solution (drug polymer) is introduced in the aqueous phase by using a syringe and drop by drop the solution is incorporated in the media while the media was still on rotation (increase the rotation to 1000 RPM before incorporation). This is done to make the solvent mixture (chloroform) to get evaporated and rigorous mixing helps in the formulation of round spherical microscope. Resultant emulsion is allowed to keep stirring at 1000-1200 RPM for about 2 hours.

In the next step, this solution formed is need to be filtered and washed. Filtration is done and the residue is washed twice or thrice with distilled water so that the remaining chloroform gets washed completely. The filter paper on which the residue (microspheres) is placed is kept in desiccator for about 24 hours and let them dry.

After drying, the formulated microspheres were collected by scraping gently using a spatula and store in air tight borosilicate glass vials.

The Emulsion microencapsulation techniques is the most suitable microencapsulation techniques. When it comes to microencapsulation, evaporation is the method of choice. employing a water-insoluble polymer to make water-insoluble pharmaceuticals.

Telmisartan microspheres produced by evaporation of emulsion solvent employing varying polymer ratios such as (Eudragit RS 100 and ethyl cellulose), and Chloroform as a solvent as well as an emulsifier. ⁷

Figure 2 Method of preparation in schematic diagram.

3. EVALUATION PARAMETERS:

I. Micromeritic Properties

a) Particle size analysis:

Size of microsphere particles were estimated by using optical microscope. A total of 100-200 microsphere particles were taken into consideration and their mean was calculated. The microscope used is calibrated. For the values, refer table-1.

b) Angle of repose (θ)

Calculated by using the formula below.

tan(θ)=h/r,

θ= tan^-1(h/r), where θ is the angle of repose

h is the height of pile and,

r is the radius of the pile

c) Bulk density and Tapped density:

Bulk and tapped density can be calculated as:

Bulk density= weight of powder/ Volume of packing .............................................................................(Eq.1)

Tapped density=weight of powder/ volume of packing .............................................................................(Eq.2)

d) Carr’s index and Hausner’s ratio:

Carr’s index compressibility can be calculated as:

CI %=tapped density-bulk density/tapped density X 100 ............................................................................ (Eq.3)

Hausner’s ratio is the collectively flow properties of powder and granules. Hausner’s ratio is the ratio of tapped density and bulk density. For the values, refer table-1. ¹⁵

Hausner’s ratio= Tapped density/Bulk density …. (Eq.4)

II. Drug entrapment efficiency, Drug yield and Drug loading:

25mg of formulated microspheres were subjected to dissolve in methanol (25ml) and the solution formed was filtered. Then dilution of filtrate was done for the analysis of drug content. The analysis of drug content was done by UV at 295nm. Following equations are used for the analysis [18]. Values are stated in Table-2 below.

Entrapment efficiency % = (Actual loading/Theoretical loading) *100 ......................................................(Eq.5)

Drug loading % = (Weight of drug in microspheres/ weight of microspheres) *100……………………(Eq.6)

Yield % = (weight of microspheres/total expected weight of drug and polymer) * 100…………………….. (Eq.7)

III. Buoyancy %

Tween 20 was present in microspheres weighing 50mg at a concentration of 0.02 w/v. A magnetic stirrer was used to stir the slurry at 100rpm. After eight hours, Pipetting is done and separation of layer of buoyant microspheres is performed and by filtering Sinking particles were separated. Filtration was used to separate the layers. Both type of particles was dried in Desiccators until they become of consistent weight. Both microsphere fractions were studied. Weighed, and buoyancy was calculated by the floating particle weight ratio to the total of Particles that float and sink^8,17. For the values, refer table-1.

IV. SEM Analysis:

SEM (Scanning electron microscopy) is the technique which is used for the estimation of the surface morphology. Formulated microspheres were coated with gold while fixed in the slabs. Figure 4 given below, infer that microsphere are completely coated with polymer and the microsphere formed are discreate and free flowing^9,16.

Figure 3 SEM image of formulation 5.

V. In-vitro dissolution studies:

In-vitro dissolution studies were examined by USP type-2 apparatus using 900ml of simulated gastric fluid (SGF) solution to maintain pH 1.2. in this process, the temperature was maintained up to 37°C. The aliquot solution is withdrawn in every 5min interval and then filtered using filter paper. The absorbance of the filtrate was measured at a maximum wavelength of 295nm. The concentration and absorbance were determined using the standard deviation curve.

The microsphere in-vitro release is studied using the USP rotating basket technique. A certain amount of microspheres were inserted in the basket, and then the basket is fitted into the 900ml dissolving vessel containing SGF medium (pH 1.2, HCl) at 37^ᵒC with the rotational speed of the paddle is 50 RPM. At 1, 2, 3, 4, 6, 12 and after 24 hours, 5ml samples were withdrawn and passed utilising a filter paper and examined using a 295 nm UV spectrophotometer calculate the Telmisartan concentration at the same time, 5ml of new dissolving fluid was added after each dissolving medium withdrawal^10,11,14. Refer table 3.

VI. Kinetic release study:

To determine the mechanism of drug release from microspheres, data from in vitro release tests were fitted to various kinetics equations (zero-order, first-order, Higuchi and Korsmeyer models) Also determined were the rate constants for the corresponding models¹². Refer table 4.

4. RESULTS AND DISCUSSION:

1. Calibration curve of telmisartan:

The standard calibration curve was estimated at phosphate buffer pH 6.8 Standard solution. Take 100mg of drug in 100ml of pH6.8 phosphate buffer to make the concentration 1mg/ml Stock solution. From the standard solution, stock solution was prepared with concentration 100mcg/ml in phosphate buffer pH 6.8. The aliquots were prepared 0.1ml, 0.2ml, 0.3ml, 0.4ml, 0.5ml, and 0.6ml solution is pipette out in 10ml volumetric flask and make up the volume upto marks. The dilutions give 0.1μg/ml, 0.2μg/ml, 0.3μg/ml, 0.4μg/ml, 0.5μg/ml and 0.6μg/ml of telmisartan respectively. The absorbance of the prepared solution of telmisartan in phosphate buffer was measured at 295nm in UV spectroscopy against phosphate buffer pH 6.8 as a blank. The data obtained from the calibration curve yields a straight line which shows that the drug follows Beer’s law. The results are given in table and figure 4 below. Co relation coefficient R²calculated is 0.9871, and the Eq for line of regression comes out to be “Y=0.0301x + 0.0118”. this equation was used to calculate the concentration of unknown for invitro^13,15.

Sl. No.	Concentration (mcg/ml)	Absorbance
0.	00	0.000
1.	01	0.001
2.	02	0.0037
3.	03	0.0139
4.	04	0.0098
5.	05	0.0162
6.	06	0.0168

Figure 4 Standard calibration curve of telmisartan in phosphate buffer pH 6.8 at λ max 295nm.

2. Physical Compatibility of Drug and Excipient:

FTIR spectra with pure drug (telmisartan) were taken alone and a peak was determined. Later pure drug with excipients was taken and spectra were determined for stability studies. FTIR used in this research work was labtronics India with KBr pellets.

Figure 5 FTIR spectra of pure drug Telmisartan.

FTIR spectroscopy is the method prefer for checking the compatibility of drug and excipients. Figure 5 depicts the characteristic peaks for telmisartan which were compared to the standard graph and there was no fluctuation seen in the graph which ensures the purity of the drug, while other spectra were also taken and studied for drug excipient interaction. FTIR studies of telmisartan along with Eudragit RS 100 and Ethyl cellulose was done and FTIR of optimised formulation was also done that infer, all the peaks were retaining their position and does not show any vibrational shifts of bands of telmisartan which infer that there is no chemical interaction between drug and polymer as shown in figure

Figure 6 FTIR spectra of optimized formulation.

Table 1- Micromeritics properties of microspheres of telmisartan.

Batch code	Particle size	Angle of repose (ᵒ)	Bulk density (g/cm³)	Tapped density (g/cm³)	Carr’s index	Hausner’s ratio
F1	197.4±16.12	24.33±0.05	0.444±0.01	0.487±0.02	8.829±0.67	1.096±0.56
F2	197.9±17.42	21.32±0.03	0.408±0.01	0.465±0.03	12.25±0.58	1.139±0.34
F3	198.2±16.02	27.54±0.05	0.416±0.02	0.487±0.01	14.57±0.13	1.170±0.51
F4	194.3±16.40	24.32±0.1	0.350±0.01	0.390±0.01	10.25±0.19	1.114±0.13
F5	198.4±16.00	29.73±0.02	0.400±0.02	0.465±0.02	13.97±0.43	1.162±0.09
F6	200.2±15.68	26.46±0.09	0.331±0.01	0.348±0.02	9.909±0.21	1.042±0.14
F7	194.5±20.23	25.29±0.09	0.400±0.01	0.444±0.01	14.26±0.19	1.110±0.11

*mean±SD (n=3)

Table 2- physiochemical properties of telmisartan microsphere.

Batch code	Drug Polymer ratio	Yield%	Theoretical drug content (mg)	Practical Drug content (mg)	Drug Entrapment (%)	Buoyancy (%)
F1	1:1:0	80±2.43	34.48±0.56	31.72±0.53	83.99±0.41	82±2
F2	1:0.5:0.5	72.5±1.78	34.51±0.98	33.1±0.91	95.9±0.32	80±2
F3	1:0.25:0.75	70±3.59	28.57±0.87	27.77±0.76	97.19±0.51	85±3
F4	1:0:1	66.66±3.13	33.35±1.77	33.02±0.35	91.99±0.52	77±3
F5	1:0.75:0.25	76.66±1.03	37.66±1.66	38.52±0.56	97.92±0.13	86±2
F6	1:1:1	72.5±1.45	38.47±1.61	37.6±0.41	97.44±0.39	85±1
F7	1:1:2	72.5±3.41	37.48±1.61	39.8±0.55	99±0.29	85±4

*mean±SD (n=3)

Table 3 – Invitro release profile.

TIME (HR)	F1	F2	F3	F4	F5	F6	F7
0	0	0	0	0	0	0	0
0.25	14.03	12.36	16.39	23.49	19.15	17.32	16.32
0.5	26.49	26.68	28.59	27.25	32.69	23.34	28.29
1	38.3	34.23	36.4	36.49	41.58	30.15	36.39
2	49.11	47.74	44.78	44.53	47.59	38.73	42.87
3	56.83	52.87	56.39	56.25	56.51	44.56	56.85
4	62.03	60.11	68.76	63.74	63.54	53.37	63.23
5	69.45	67.78	72.45	68.91	75.65	60.98	70.65
6	76.09	75.98	74.98	75.88	81.64	66.49	77.23
12	80.88	83.26	80.86	78.39	88.64	74.33	84.44
24	86.32	88.9	87.53	80.02	92.83	83.32	86.39

Figure 7 invitro drug release profile (F1-F7)

Table 4 – invitro release profile fitted in various models.

Batch code	Zero order (r²)	First order (r²)	Higuchi (r²)	Korsmeyer (r²)	N (slope)
F1	0.5392	0.2291	0.8271	0.8989	0.6037
F2	0.5866	0.2491	0.861	0.9137	0.6118
F3	0.5389	0.2264	0.8252	0.8913	0.598
F4	0.4947	0.2024	0.7917	0.8573	0.573
F5	0.566	0.2215	0.8446	0.8764	0.5952
F6	0.6498	0.258	0.9024	0.9034	0.5803
F7	0.5477	0.2309	0.8331	0.8944	0.5982

5. CONCLUSION:

Telmisartan floating microspheres were prepared using different ratio of polymer Eudragit RS 100 and Ethyl cellulose using solvent evaporation method.

By performing calibration, we infer that telmisartan showed maximum absorbance at 295nm. Further FTIR studies were conducted that infer that there is no interaction between drug and other excipients. Floating microspheres loaded with drug were studied to know about the yield%, %drug entrapment efficiency and % buoyancy. The results depicted the range from 66.66±3.13 to 80±2.43, the range for % drug entrapment comes out to be 83.99±0.41 to 99±0.29 and for buoyancy % 77±3 to 86±2.The release profile concluded that f5 showed maximum release of 92.83% by which it can be estimated that drug polymer ratio of 1:0.75:0.25 (Drug: Eudragit RS 100 : Ethyl Cellulose) is the one showing the best release, and by fitting the invitro data into various kinetic models it was concluded that F1 to F7 is following zero order as it is having high linearity value (r²) . The slope value obtained from korsmeyer peppas plot ranges between (0.573- 0.6118) which infer that the formulation is showing Anomalous (non fickian) type of diffusion. F5 formulation follows korsemeyer peppas (non fickian diffusion) confirms the best controlled release. From the study and the results depicted, it is concluded that the particles formed were in mm range having greater yield, good entrapment efficiency, good buoyancy capability, and it will perform steady and prolong release of drug which was required.

6. CONFLICT OF INTEREST:

Declared none.

7. REFERENCES:

1. Jagtap, Yogesh and Bhujbal, Rohan and Ranpise, Nisharani. (2012). Floating microspheres: A review. Brazilian Journal of Pharmaceutical Sciences. 48. 17-30. 10.1590/S1984-82502012000100003.

2. Varma Kumar Ajit, Gupta Kumar Arun, Khare Piush, Patel Rakesh. Formulation and Development of Floating Microspheres containing Levodopa and Carbidopa. Asian J. Pharm. Tech. 2018; 8 (4):200-202

3. Rohilla S, Bhatt DC, Ahalwat S. Fabrication of potential gastroretentive microspheres of itraconazole for stomachspecific delivery: Statistical optimization and in vitro evaluation. J Appl Pharm Sci, 2020; 10(03):119–127

4. Kendre, Prakash and Chaudhari, Pravin. (2012). Formulation and Evaluation of Telmisartan Microspheres by Solvent Evaporation Technique.

5. Rahul Rawat, Yogesh Josh. Effect of Antihypertensive Drugs on Homocysteine level among Hypertensive Patients. Asian J. Res. Pharm. Sci. 2018; 8(4): 219-222

6. Sonali S. Jaiswal, Shashikant D. Barhate. Formulation Optimization and Evaluation of Immediate Release Tablet of Telmisartan. Asian J. Res. Pharm. Sci. 2019; 9(3):167-173.

7. Praveen Kumar Gaur, Shikha Mishra, Meenakshi Bajpai, Formulation and evaluation of controlled-release of telmisartan microspheres: In vitro/in vivo study, Journal of Food and Drug Analysis, Volume 22, Issue 4,2014, Pages 542-548, ISSN 1021-9498, https://doi.org/10.1016/j.jfda.2014.05.001.

8. Jinukula Bhavani, Shah Saloni and Dhurke Rajeshri. 2019, Formulation and Evaluation of Floating Microspheres Using Factorial Design. Int J Recent Sci Res. 10(12), pp. 36363-36370. DOI: http://dx.doi.org/10.24327/ijrsr.2019.1012.4908

9. Celli GB, Ghanem A, Brooks MS. Development and evaluation of floating alginate microspheres for oral delivery of anthocyanins – A preliminary investigation. Food Sci Nutr. 2017; 5:713–721. https://doi.org/10.1002/ fsn3.451

10. Krutika Sawant, Mitali Patel, Jiten Patel, Piyush Mundada. Formulation, optimization, characterization and in vivo anti-ulcer activity of esomeprazole magnesium trihydrate gastroresistant microspheres. Int J Pharm Pharm Sci 2017;9(1):273-282

11. Design, Formulation and in vitro Drug Release from Transdermal Patches containing Nebivolol Hydrochloride as Model Drug. Asian J. Pharm. Res. 2(4): Oct. - Dec. 2012; Page 136-141.

12. Vanitha Kondi, Ramesh Alluri. In Vitro and In Vivo Evaluation of Floating Microspheres of Prazosin Hydrochloride. Asian J. Pharm. Tech. 2016; 6(4): 202-206.

13. J.M. Chavda, M.A. Raval, K.R. Dave. Simultaneous estimation of Telmisartan and Indapamide in Bulk Drug and in pharmaceutical dosage form using UV-Spectrophotometry. Asian J. Research Chem. 5(9): September, 2012; Page 1129-1135.

14. Shanmugam. S., Sandhiya. K. M., Ayyappan. T, Sundaramoorthy. K., Vetrichelvan. T. Design and In Vitro Studies of Ambroxol Hydrochloride Sustained Release Matrix Tablets. Research J. Pharma. Dosage Forms and Tech. 2011; 3(2): 48-52.

15. Shahana. V. P, Gayathri Ramya M, Rajesh A, Kathirvel. S. A Comprehensive Validation Method and Development of RP-HPLC for Simultaneous Estimation of Metoprolol, Telmisartan and Chlorthalidonein Bulk and its Formulation. Asian J. Research Chem. 2018; 11(6): 827-834.

16. Manish P Patel, MM Patel, KN Patel, DR Patel, UL Patel. Designing and Evaluation of Floating Microspheres of Verapamil Hydrochloride: Effect of Methocel. Research J. Pharma. Dosage Forms and Tech. 2009; 1(1): 22-28

17. Sethi RK, Sahoo SK, Das PK, Barik BB. Effect of Dispersing Agent on the Characteristics of Eudragit Microspheres. Research J. Pharma. Dosage Forms and Tech. 2010; 2(1):67-71.

Received on 02.07.2022 Modified on 14.08.2022

Res. J. Pharma. Dosage Forms and Tech.2022; 14(4):283-288.

DOI: 10.52711/0975-4377.2022.00046